“We are very much scared,” says Hamid Aftan al-Hammad, an Albu Nimr tribesman from the city of Hit in western Iraq. “At night we lie on the roofs of our houses with our weapons waiting to be attacked again.”

He fears the return of Isis, which massacred at least 864 members of his tribe when they controlled the area where they live – a city a hundred miles west of Baghdad in the middle of the vast Sunni Arab province of Anbar, which sprawls across western Iraq.

“It was there that they killed 45 of our people,” he says, going on to list those members of his immediate family who were murdered, including two teenage cousins executed in the main square of the city and two uncles who tried to escape into the desert but have disappeared and are assumed to have been captured and killed by Isis.

Compared even to the many other Isis atrocities, the hunting down of the Albu Nimr, a pro-government Sunni tribe, was relentless and genocidal.

Sala Segur Omar al-Nimr, a teacher who lived through the final months of his tribe’s resistance, described how they dug trenches and built sand barriers in a hopeless attempt to defend themselves, but it was not enough.

They faced thousands of better armed Isis fighters. When resistance finally collapsed in October 2014 those who could not flee fast enough “were slaughtered, many of them elderly, disabled or very young children. They even killed our farm animals.”

There is little violence today in Hit, a city with a population of 90,000 people. But the hatred and fear generated by the savage rule of Isis still divides its people.

Borhan Khalil, a local journalist, says that “there is still this division between pro- and anti-Isis families”. Foreign fighters may have belonged to Isis, but the great majority were locals and longtime neighbours of those they killed.

Mr Khalil says that families whose houses were blown up by Isis – often because they had worked for the Iraqi government – have frequently taken over, with official approval, the houses of Isis supporters who have since fled.

This is a further cause of anger and division.

The change of ownership is announced by messages scrawled on the outside wall of a house. One such message by a gate in central Hit reads: “This is the house of the fleeing terrorists now occupied by Fuad and his brother.”

Inside the house, which looks spacious and well kept, Haitham al-Ad al-Nimr, a member of the government security services, and his brother Fuad have been living there since they took it over a year ago.

“Our own house was completely demolished by Isis,” says Mr Nimr, who denies that he knows the identity of the people he has replaced. He explains that “they had fled long before we got here”.

He is not worried by the prospect of the dispossessed trying to take their property back one day, or of Isis launching a successful counteroffensive in Anbar.

Others are not so sanguine: Hamid Aftan al-Hammad, whom we met when he was about to cross the Euphrates in a boat because the bridge had been destroyed, says Isis families whose sons had been fighters were coming back to the area and, even if the fighters were not with them, they “will still back their sons”.

The Iraqi government is trying to defuse the issue of what happens to families with a record of supporting Isis in the past, but without much success.

This is particularly true in Hit, where the Albu Nimr reckon they lost about 1,000 people, with the same number of disappeared, shot in the desert as they tried to escape, or had their bodies thrown down wells.

Mr Hammad is enraged that two of his brothers had been thrown out of a house they had taken over and were now living in tents because a family they alleged were Isis supporters had now reoccupied it.

He says they deserved better from a government they had fought for: “One of my brothers has a crippled arm and lost three fingers when he was shot by an Isis sniper.”

Why was Isis so determined to wipe out this particular tribe? Isis certainly wanted to show that any resistance to them would provoke pitiless revenge. The Albu Nimr were an obvious target because their tribesmen had joined the army and police after the US-led invasion of 2003.

They did so at a time when the other Sunni tribes of Anbar were at the heart of resistance to the US occupation and the Shia-dominated government in Baghdad.

As Isis made its spectacular advance in 2014, the Albu Nimr were isolated, outgunned and outnumbered.

Once Isis seized Mosul and the Iraqi army in northern Iraq disintegrated, the jihadis were able to capture plenty of heavy weapons.

The Albu Nimr say they begged the government and the Americans for arms and airstrikes but received nothing.

Well-off people in Hit were able to flee but those without money were forced to stay and endure Isis rule.

They say this was so cruel and murderous that Isis lost its popular support. Mr Khalil believes that everybody in Anbar – and not just the Albu Nimr – would today fight Isis because “Isis denounces everybody in government-held Iraq, which these days is almost the whole country, as infidels who deserve to be killed, so nobody wants them back”.

This is comforting, but Isis is a fanatical militarised cult that has never sought popularity and spreads its faith through force.

The terror it inspired in the past still lives on: a small surge in Isis killings and kidnappings in recent weeks reverberated throughout Iraq.

People in Hit say they have confidence in the Iraqi army as non-sectarian, but they know that Sunni Arabs are regarded with suspicion.

“As soon as I travel outside Anbar and show my Anbar ID at a checkpoint, I am held for hours,” says one source.

The Sunni of Iraq, a fifth of the population who had ruled the country for centuries, have shared in the Isis defeat and are politically marginalised.

Sunni cities like Mosul, Ramadi and Fallujah are badly damaged, though there are signs of revival and reconstruction. The bridge across the Euphrates at Hit, destroyed by an airstrike by the US-led coalition, is being rebuilt and will reopen in a couple of months.

Ramadi, the capital of Anbar, suffered worse damage than Hit, and heaps of smashed concrete floors and walls stand where schools and villas used to be.

The price of property has halved in Anbar since the pre-Isis era, but in many places new houses and offices have been rebuilt, or yellow bulldozers and construction equipment can be seen clearing the rubble. The physical damage may be disappearing with surprising speed, but Isis rule has left a legacy of hatred that is still very present.